Short-term use of a level of estrogen designed to mimic pregnancy may be highly effective in protecting women from breast cancer, according to research presented at the American Association for Cancer Research's first annual Frontiers in Cancer Prevention Research meeting.

A full-term pregnancy at an early age is the only natural physiological condition known to significantly decrease the lifetime risk of breast cancer in women of all ethnicities. This study's findings show that when given one microgram of estradiol per day for three weeks, rats that had not previously had babies had no mammary cancers nine months after being injected with chemical carcinogens.

"We found that daily sustained treatment with pregnancy levels of estrogen for three weeks is a simple, safe, short-term, inexpensive procedure for hormonal prevention of mammary cancer," said Rajkumar Lakshmanaswamy, research assistant and lead investigator of the study conducted at the University of California at Berkeley. "This procedure is as effective as full-term pregnancy, removal of the ovaries or long-term tamoxifen treatment, without any loss of ovarian function including the potential for future successful pregnancies and lactation."

Full-term pregnancy in human, like in rats, results in a long-term decrease in blood levels of growth hormone and prolactin, resulting in a reduced environment that would promote the development of breast cancer.

"The study concluded that this treatment can be used as a paradigm for developing strategies for human breast cancer prevention," concluded Lakshmanaswamy.

Other sources: American Association for Cancer Research